The field of the invention relates to integrated circuits such as processor circuits, digital logic circuits, mixed-signal integrated circuits, analog circuits and ASICs (application specific integrated circuits) and to other circuits that connect to battery chargers, batteries, and other power sources such as for electronic devices generally, and pertains to battery management and/or power management circuitry for mobile devices and wireless devices. Some forms of such circuitry may connect to a USB (universal serial bus) type of charger or other possibly-low-current type of charger.
USB charging for mobile equipments has became very popular, especially in Asia and Europe where it has been promoted as a universal charging solution by the Chinese government and the European Commission. USB charging potentially can offer user convenience and economy if it can make a separate battery charger unnecessary for one or more battery powered devices. Both the charger adapter and mobile equipment sides of USB charging systems are specified by standards like the Battery Charging Specification version 1.2 accessible at http://www.USB.org. Specified electrical requirements as well as detection and control mechanisms are supposed to guarantee system functionality, manufacturer interoperability and seamless user experience.
USB, originally for the personal computer PC industry, allows many peripherals (devices) to be connected to a PC host for serial data transfers. USB can provide power as well to the devices via a tiered star topology, wherein a device is connected to a hub through a downstream port. Hubs may provide several downstream ports and a single upstream port, and hubs can be cascaded to provide many downstream ports for devices. Hubs provide power on ports through a VBUS bus line. USB port power capability is specified in unit loads, where one unit load can be 100 mA (milliamperes of electrical current). In a self-powered hub, externally-sourced power (often up to five 5 unit loads) goes to the USB downstream port, and the hub itself may also draw up to 1 unit load. In a bus-powered hub, power comes on a bus from the facing USB port, e.g. up to 5 unit loads; and power is then split for downstream ports and hub internal power. Self-powered and Low-powered devices may receive power up to one (1) unit load, and High-powered devices may receive up to five (5) unit loads. These definitions of port power consumption and capabilities might result in insufficient power for some devices or in some scenarios.
Using charger power or USB power to charge a battery can be vital to support primary device functions such as providing mass storage for documents, transferring multimedia content, calendar and email synchronization, modem accessing a global network, printing, GPS positioning, etc. Accordingly, the device might be set up in a recognized manner to report no more than one (1) unit load during a reporting process called enumeration to get supported by a USB system upstream. But with present battery capacities in the 1 Ah (ampere-hour) range, a five (5) unit load downstream port capability would be desired when possible. Host can choose the power configuration depending on its downstream port power capability as well as its own energy management, but may be prevented by its operating system from supporting some multiple configurations, and may also be influenced by a suspend state in the host. A dead battery might not only prevent a device from enumerating, but leave host prevented from charging it.
In an OTG 2.0 technology, power is provided to the bus VBUS or receives the power from the bus. In a Session Request Protocol (SRP) host can decide to un-power and restore power to the VBUS line. In OTG, host is called an A-device that always provides power to bus, and a peripheral is B-device that always receives power from a bus; and these roles can be negotiated. Some applications include connecting USB headset to a mobile phone or MP3 player, or a pod providing power and speakers for MP3 player, a docking station providing power to USB peripherals, a car kit providing a large touch-screen display and battery charging, and/or direct connection between two portable devices for file exchange, synchronization, connecting mass storage, etc.
For example if a battery powered mobile acting as A-device detects a headset, it could allow 100 mA to it. If the same A-device detects a battery powered peripheral reporting multiple power configurations, it might choose to provide no current at all. And if the same A-device detects a 500 mA PC mouse, it might shut down its VBUS and inform user of a non-supported peripheral.
Also, a number of low-cost charger adapters may comply with a country's specifications but be outside standard specifications in some other country. Some marginal or low-cost charger adapters may not comply with any particular standards at all, and might proliferate in emerging market areas with at least some penetration in more-developed market areas of the world as well. In systems where it is possible to supply a processor or other functional circuit directly with the charger adapter without the battery being previously charged, such systems might detect and identify the charger adapter to make sure it can deliver enough power for supplying the system. In such case, a charger identification status signal could be used as an input as a condition to be met before permitting the device to power-up. If a marginal or non-standard charger adapter can defeat the charger adapter identification process so that charger adapter identification process results in wrong identification of a marginal or non-standard charger adapter as allowable, then such identification-based system may take the decision to power-up and then crash the system. This problem can happen especially with USB charger adapters because of their potentially-insufficient current for charging particular systems or in particular scenarios. Moreover, a low-current charger adapter of whatever type may crash a device if use is attempted with or without concurrent charging of the device battery. If a system is arranged to not thus permit the charger adapter to supply the system, the user is left unable to use the system while the battery is being charged even by an adequate charger or in a scenario where sufficient current is indeed available.
A problem for mobile equipment makers thus is to provide users with mobile devices and other types of electronic devices that can support low-current chargers generally and this wide variety of charger adapters that have unknown or less than fully known characteristics or that may be insufficient on a scenario-specific basis, without affecting device robustness and user experience with chargers defined by and compliant with industry standards. Accordingly, significant technological departures are called for and would be most desirable in this technology field.